The present invention relates to an electromagnetic device using a solid matrix layer wherein micro-capsules each containing suspension of anisotropic particles are dispersed, and more particularly to an electromagnetic device of large area applicable to a cell with the controllability of transmission, so-called smart window, permeation-type indication element. Reflection-type indication element and the like used for architecture and vehicles, wherein the transmittance or reflection of solar radiation of device are electrically controlled.
As a device using micro-capsules, there has been known a liquid crystal comprising micro-capsuled nematic liquid crystal (hereafter refereed to as NCAP). Further, it is considered that an electrochromic element (hereafter referred to as EC element) is useful for the smart window which enables to lessen the load of air-conditioner by electrically controlling the transmittance of solar radiation (hereafter referred to as T.sub.G) since the EC element changes the T.sub.G by electrochemical oxidation-reduction reaction of the electrochromic films (C. M. Lampert, Solar Energy Mater, 6 (1981) 1). In addition, as an element having controllability of the transmittance in the visible region, there has been provided by A. M. Marks an electromagnetic device comprising a suspension containing particles such as vanadium pentaoxide and lead carbonate, and electrodes sandwiching the suspension (hereafter referred to as DPS element) (U.S. Pat. No. 3,257,903 (1966)).
After that, the research of DPS elements has been performed and advanced by the group of Research Frontiers Inc.. The group reported that particles of hydrogenated herapathit were adaptable to DPS elements (U.S. Pat. No. 4,131,334(1977)).
NACP has a great advantage that a device having large area can be fabricated with maintaining high response rate of liquid crystal. In optical point of view, however, NACP has only switching function between transparent and milky (light scattering) states. Thus, NACP is applicable to a curtainless window and the like, but it is not applicable to the smart window requiring continuous control of T.sub.G. To the contrary, the EC element has controllability of transmission, but it has such disadvantage as its response speed becomes remarkably slow and uniform light control cannot be obtained when the area becomes large, since its controllability of transmission depends on electric current.
Further, the DPS element is liquid, so that it has optical nonuniformity caused by partial nonuniformity of thickness and particle density. The nonuniformity of thickness is caused by the falling of liquid due to the gravity when the DPS element is arranged in a vertical state assuming its use for windows. The nonuniformity of particle density in a vertical direction is caused by sedimentation of anisotropic particles (generally made of metal or metal oxide) due to the difference of specific gravity between the anisotropic particle and solvent. Further, it is difficult for DPS elements with the above-mentioned disadvantages to be applied to a smart window having a large area, since the nonuniformity of thickness and particle density are promoted with the increase of area of the element.
Still further, the conventional DPS elements hardly have the ability of absorbing and reflecting light of visible and near infrared region. The absorbed and reflected wavelength band is narrow even if such light is absorbed or reflected. As a result, the conventional DPS element is suitable only for curtainless windows, but not suitable enough for smart window because of the lack of controllability of T.sub.G.
To the contrary, the DPS element using hydrogenated herapathit has a good controllability of transmission, since it has strong light-absorbing ability for visible region. For the use of the window glass, however, DPS element has a problem in weatherproof ability since hydrogenated herapathit is organic compound.
It is accordingly an object of the present invention to solve the above-mentioned problem, i.e., to provide an electromagnetic device comprising solids or semisolids wherein micro-capsuled anisotropic particle suspension is contained, and a means for applying electric field or magnetic field to the anisotropic particles.